The present invention relates to downhole drilling, such as downhole drilling technology for oil, gas, geothermal and horizontal drilling. More specifically, the present invention relates to downhole drill string components and connections between components. Also, the present invention relates to communication between uphole and downhole components.
Downhole instruments may be used to analyze downhole formation characteristics such as porosity or density, or to locate resource deposits in a formation. The assembly of a drill string having a plurality of instruments often involves electrically connecting the instruments individually. In many cases, each instrument must be wired separately. Downhole drill strings with multiple instruments can have a multiplicity of wires, often increasing the complexity of wiring downhole instruments to the desired location within the drill string. The overall efficiency of this method of wiring may be inferior to an apparatus that reduces the number of wires involved. Additionally, an apparatus with the ability to simultaneously electrically connect the plurality of instruments to a power source, processor, or a downhole network may reduce the assembly time of the drill string.
A common practice in the art involves exciting one instrument that is circumferentially wrapped around the drill string and used to gather borehole data downhole. Exciting this single instrument generally does not allow for only a portion of a borehole to be analyzed to determine downhole characteristics.
U.S. patent application Ser. No. 11/776,447 to Snyder, which is herein incorporated by reference for all that it contains, discloses an induction resistivity tool incorporated into a downhole tool string. The induction resistivity tool comprises an outer wall of a downhole component having an outer surface and at least one induction transmitter assembly disposed along the outer surface. The at least one transmitter assembly has at least one induction transmitter coil wound about at least one core. The at least one induction transmitter coil is adapted to project an induction signal outward from the outer wall when the at least one induction transmitter coil is carrying an electrical current. The transmitter assembly is adapted to create electromagnetic fields that originate the induction signal from outside the outer wall and substantially prevent the signal from entering the outer wall.
U.S. Pat. No. 5,045,795 to Gianzero, et al., which is herein incorporated by reference for all it contains, discloses a coil array that is installed on a MWD drill collar for use in a resistivity logging system. The drill collar is provided with upper and lower coil support rings. The coil support rigns are toroids which support individual coil segments, and are connected by suitable magnetic shorting bars. The coil segments and shorting bars inscribe a specified solid angle or azimuthal extent. By connecting the outputs of the several coils through a combining circuit, the coils on a single support ring can be connected in series additive, or subtractive relationship. Through the use of two such coil support rings with aligned coils on each, an azimuthally oriented window is thereby defined. By proper switching multiple azimuthally oriented windows can be made operative so that there is an azimuthal orientation to the current flow pattern relative to the MWD resistivity logging tool.